It is specified in the industry that a high speed shared control channel (High Speed Shared Control Channel, HS-SCCH) is ahead of a high speed physical downlink shared channel (High Speed Physical Downlink Shared Channel, HS-PDSCH) by 2 slots (Slot). The objective of such a specification is to facilitate a user equipment (User Equipment, UE) to use the 2 slots to first detect a Slot1 portion of the HS-SCCH. If the detection succeeds, it indicates that a transmitted sub-frame is the sub-frame belonging to the UE. Then the UE decodes data of Slot2, and begins a process of buffering demodulation data of the HS-PDSCH. Therefore, correct detection of the HS-SCCH Slot1 is of great importance for throughput and power consumption of the UE.
In the prior art, the YI algorithm is generally used for the detection of the HS-SCCH Slot1.
The YI algorithm is mainly to trace and mark a path in the process of Viterbi (Viterbi) decoding. A method for marking the path of each state in each step is: selecting a path a that enters the state and has a maximum likelihood path metric and a path b that enters the state and has a sub-maximum likelihood path metric. If a difference between the path metric of a and the path metric of b is greater than or equal to a threshold A, the path a is marked as C; otherwise, the path a is marked as X, and all other paths other than a are discarded. An optimized path of each state in every step is selected in such a manner till a final level. The process for detecting the HS-SCCH Slot1 using the YI algorithm is described below with reference to FIG. 1.
As shown in FIG. 1, it is assumed that 4 reserved paths for 4 states 0, 1, 2, 3, at a level j−1 are respectively a, b, c, d, and are all identified as C.
It can be seen from FIG. 1 that at a level j, paths a-e and are incorporated into the same node of state 0, and paths b-g and d-h are incorporated into the same node of state 2.
Ifλj(a−e)−λj(c−f)≧A 0<(λj(b−g)−λj(d−h))>A 
where λj (a−e) is a maximum likelihood path metric of the path a−e, λj(c−f) is a maximum likelihood path metric of the path (c−f), λj(a−e)−λj(c−f) is a path metric difference (Path Metric Difference, PMD) of the node of state 0 at the level j, and A is a threshold;
λj (b−g) is a maximum likelihood path metric of the path (b−g), λj(d−h) is a maximum likelihood path metric of the path (d−h),
λj(b−g)−λ1(d−h) is a PMD of the node of state 2 at the level j;
then the path a−e is identified as C, the path b−g is identified as X, that is, at the level j, the node of state 0 is marked as C, and the node of state 2 is marked as X.
As shown in FIG. 1, at a level j+1, a path a−e−s and a path b−g−t are incorporated into the same node of state 0; that is,λj+1(b−g−t)≧λj+1(a−e−s)+A 
where λj+1(b−g−t) is a maximum likelihood path metric of the path (b−g−t), and λj+1(a−e−s) is a maximum likelihood path metric of the path (a−e−s).
The path b−g−t is still identified as X, because at the level j, the path b−g has been identified as X. The process is repeated till the decoding is completed. At the final level, if a survival path with the maximum path metric is identified as X, or a node in a backtracing path is marked as X, the detection is considered as a failure; otherwise, the detection is considered as a success, and (“success”) is output.
The process may be briefly described as follows: In the YI algorithm, the HS-SCCH Slot1 is detected by judging whether the PMD on a certain node is greater than a threshold. At present, the YI threshold is mainly a fixed threshold obtained empirically and through lots of emulations.
During the implementation of the present invention, the inventors find that the prior art at least has the following problems. In a practical signal environment, due to the influence of channels and interference, received signals fluctuate greatly, so that using a fixed threshold in detection is inapplicable for the situation of multiple signal environments, and therefore the detection performance for the HS-SCCH Slot1 is decreased.